The health secretary, Alan Milburn, will today announce that some NHS patients who have waited for more than six months for operations will soon be able to obtain treatment in a hospital of their choice - public or private - in Britain and eventually in Europe.

The revolutionary move will be the latest step in the government's drive to reform the delivery of health service, the momentum of which has dramatically increased in the past two weeks.

The innovation will start in London, which has some of the longest waiting lists. Mr Milburn will allow patients with some categories of illness to go elsewhere for treatment, probably from April onwards in a pilot scheme.

Up to 45,000 patients in London and the south-east are expected to benefit in a policy shift designed to help transform Aneurin Bevan's 1948 model of health as a nationalised industry into a more user-friendly public service.

"We are letting the genie out of the bottle, though we are doing it slowly and steadily. Once it is out of the bottle it won't be possible to get it back in again," one policy maker predicted last night.

Ministers have promised that by 2004 no one will have to wait more than six months for an operation, as waiting times are brought down step by step, thanks to an anticipated increase in doctors, nurses, equipment and capacity. A booking system for treatment is also promised.

At first the policy is expected to be aimed at speeding treatment for patients waiting more than a year, including thousands of people needing hip and knee replacements or cataract surgery.

Latest Department of Health figures for September showed 10,300 patients in England waiting more than 15 months. This was 20.7% lower than a year before and ministers said they were confident of meeting a target to eliminate 15-month waits by early next year.

At that point the government's priority will become the 12-month waiters - about 43,900 at the latest count. The eventual target is to bring maximum waits down to six months by 2005.

Problems that Mr Milburn will have to address in a Commons statement today will include how to ensure that long waiters with the greatest clinical need get treated first, instead of being overtaken in the queue by those with the most eloquent GPs or combative relatives.

The health secretary will also have to devise a speedier method of paying hospitals taking patients from outside their normal catchment areas. Under current procedures the money can take up to two years to follow the patient.

The government's enthusiasm to reform the provision of health services has led in the past two weeks to a deal with the private health provider Bupa and the promise of more money to raise UK spending on health to the European average.

The Bupa deal, under which a private Surrey hospital will become a dedicated NHS diagnostic and treatment centre, is part of the health secre tary's drive to shake up NHS practices. Treatment will remain free and based on clinical need but the NHS's role as a near-monopoly provider of health care in Britain looks set to be further eroded.

In a separate development, which followed a European court ruling, Mr Milburn has already conceded that, where there are severe delays, more patients will be allowed to get treatment in France or Germany where richly-funded health systems have spare capacity - the opposite of Britain's cash-starved NHS.

Both changes are designed to raise performance, not least by exposing what Whitehall regards as Britain's over-expensive private health sector to competition from more efficient EU rivals. Thanks to new performance league tables NHS hospitals are also under pressure to do better.

Today's move comes as Tony Blair and Gordon Brown are throwing huge extra resources at the NHS. In the Commons today Mr Milburn will allocate the extra £1bn given to the NHS by the chancellor last week when he unveils rapidly revised budgets for health authorities.

With voters increasingly dismayed at the NHS's poor performance all the parties now see it as the key battleground for the coming years.

Believing that Labour's "Stalinist" NHS plan is doomed, the Tories are edging towards private insurance for the better off.

Yesterday in the Commons Iain Duncan Smith, the Tory leader, taunted the prime minister over the exact sums needed to meet his promise to raise UK health spending to the EU average - 8% according to Whitehall, nearer 10%, say outside experts. Mr Blair countered that the Tories want to abolish the NHS.